From ee526b88caaa4b4182144bf2576af2c3b1e9c759 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Tue, 24 Oct 2023 14:46:58 -0400 Subject: closures: Fix race in closure_sync() As pointed out by Linus, closure_sync() was racy; we could skip blocking immediately after a get() and a put(), but then that would skip any barrier corresponding to the other thread's put() barrier. To fix this, always do the full __closure_sync() sequence whenever any get() has happened and the closure might have been used by other threads. Signed-off-by: Kent Overstreet --- lib/closure.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'lib') diff --git a/lib/closure.c b/lib/closure.c index 501dfa277b59..f86c9eeafb35 100644 --- a/lib/closure.c +++ b/lib/closure.c @@ -23,6 +23,8 @@ static inline void closure_put_after_sub(struct closure *cl, int flags) if (!r) { smp_acquire__after_ctrl_dep(); + cl->closure_get_happened = false; + if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) { atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER); @@ -92,6 +94,7 @@ bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl) if (atomic_read(&cl->remaining) & CLOSURE_WAITING) return false; + cl->closure_get_happened = true; closure_set_waiting(cl, _RET_IP_); atomic_add(CLOSURE_WAITING + 1, &cl->remaining); llist_add(&cl->list, &waitlist->list); -- cgit v1.2.3-58-ga151